An agricultural harvester, also referred to as a combine or combine harvester because it typically combines multiple harvesting functions, typically includes a header for removing a crop from a field and a so-called threshing tool for performing a threshing operation on the crop in order to separate the grain from the non-grain material such as straw. The non-grain material may subsequently be transported from the threshing tool to a residue processing tool such as a chopper, e.g. a straw chopper. Such a residue processing tool typically reduces the size of the non-grain material and direct it out of the rear of the combine. This chopped non-grain material or chopped crop residue typically remains on the field and serves to fertilize the field. In order to do so, it is important that the size of the chopped crop residue particles as outputted on the field is sufficiently small. At present, the quality of the chopped crop residue, in particular the size or length of the chopped crop residue, is typically checked manually by the operator of the harvester, whereupon, when needed, operating parameters of the residue processing tool may be adjusted. This is typically done once a day or even less. Because crop conditions may vary significantly over time or may be location dependent, the quality of the chopped crop residue may vary significantly as well. Therefore, in order to maintain a good quality of the chopped crop residue, the operator should preferably check the quality of the chopped crop residue more often, resulting in a more time consuming harvesting process. As such, there is a need to provide in an alternative way of assessing the quality of the chopped crop residue that is less time consuming.